A capo is a device which allows the player of a fretted instrument, such as a guitar, to temporarily raise the pitch of the instrument. The capo is attached between frets on the neck, or fingerboard, of the instrument thereby clamping all of the strings on the fingerboard at a desired fret location, so that the unfingered pitch of all the strings is raised. Assume, for example, that a particular song is best played in the key of "D", because certain sounds and colorations of the song can only be achieved with techniques in the key of "D". It could be, however, that the vocalist can best perform the song one step higher on the musical scale, in the key of "E", because of his voice characteristics. By using a capo to clamp the guitar strings between selected frets, the guitar player can play the song with the "D" chord progression and techniques while allowing the vocalist to sing in the more comfortable key of "E".
Prior capo designs have generally suffered from a common deficiency. Many stringed fretted instruments, such as guitars, have strings which vary in thickness progressively from one side of the fingerboard to the other. When certain of the prior capo designs are adjusted to hold down all the strings properly, the larger diameter strings are "clamped" or "squeezed" tighter than the smaller diameter strings. As a result, the larger diameter strings are elevated in pitch past the point of relative pitch with the other strings which are squeezed. Thus, a performer who uses a traditional capo on a tuned guitar during a performance will often have to stop temporarily to retune the guitar to compensate for the effect of the capo.